Centrifugation device

ABSTRACT

A centrifugation device comprising a combined sample chamber and slide holder adapted to be mounted, with a microscope slide, in a centrifuge in a predetermined position, after placing, in the sample chamber, a fluid biological sample containing cells, the centrifugation device comprising a body ( 10 ) affording a base ( 14 ) adapted for engagement with a microscope slide, structure on one side of the base defining a chamber for a fluid sample, with an opening ( 15 ) for the introduction of fluid to said chamber, the base ( 14 ) including an aperture ( 18 ) and carrying a means for sealing the edges of such aperture with respect to the surface of a microscope slide placed across the base ( 14 ), or for allowing the passage of liquid but obstructing the passage of cells, the centrifugation device further including a back plate ( 12 ) arranged, when the back plate ( 12 ) is closed against the rear of a microscope slide engaged with the base ( 14 ), to locate the slide between the base and the cover plate and to hold the cover plate in this closed position, wherein said base ( 14 ) comprises a supporting frame ( 17 ) and, within said support frame, a pressure plate ( 19 ) provided with said aperture ( 18 ), and wherein the pressure plate is supported from said frame by flexible resilient means ( 40, 42 ) such as to allow the pressure plate to “float” and to align itself with a microscope slide located between the pressure plate and the back plate as the back plate is closed.

RELATED APPLICATIONS

This is a U.S. national phase of PCT/GB2004/001904 filed 5 May 2004,claiming priority from GB 0319709.2 filed 21 Aug. 2003.

THIS INVENTION relates to a centrifugation device comprising a combinedsample chamber and slide holder adapted to be mounted, with a microscopeslide, in a centrifuge in a predetermined position, after placing, inthe sample chamber, a fluid biological sample containing cells, thedevice being so-arranged that when the centrifuge is operated, a thinlayer—ideally a monolayer—of cells is deposited from the fluid-onto apredetermined deposition area on the glass microscope slide; Such acentrifugation device is herein referred to as being “of the kindspecified”.

Various forms of centrifugation device of the kind specified have beenknown in the past. Examples of such devices are disclosed, for example,in U.S. Pat. Nos. 4,391,710; 4,696,743; 4,853,188 and 4,874,582 andEuropean Patents Nos. 0184374 and 0047840. Some examples have beenreusable, that is to say it was possible and intended that after thedevice had been used to deposit cells from a fluid sample onto a firstmicroscope slide, and the slide removed, the device could be cleaned, afresh slide fitted, a fresh fluid sample placed in the sample chamberand the device again placed into the centrifuge and so on indefinitely.In these arrangements the slide is, of course retained by a releasableand re-attachable clip of some description. Some later centrifugationdevices of the kind specified were of the single-use type, that is tosay they were designed in such a way that they could not, or could notconveniently, be used more than once, thereby avoiding contaminationproblems resulting from improper cleaning procedures between uses. Inview of their inevitably disposable nature, devices of the lattercharacter have generally been largely of plastics in order to minimiseproduction costs.

A centrifugation device of the kind specified generally comprises acombined sample chamber and slide holder adapted to be mounted, with amicroscope slide, in a pre-determined position in a centrifuge afterplacing, in the sample chamber, a fluid biological sample containingcells, the centrifugation device comprising a body affording a baseadapted for engagement with such microscope slide, structure on one sideof the base defining the sample chamber with an opening for theintroduction of fluid to the sample chamber, the base including anaperture for communicating with the sample chamber and the base carryingmeans for sealing the edges of such aperture with respect to the surfaceof the microscope slide placed across the base, or for allowing thepassage of liquid but obstructing the passage of cells. Such acentrifugation device further typically includes, a back plate hingedlyconnected with the base, or otherwise securable to the base.

A problem which arises, particularly in relation to single use, mouldedplastics centrifugation devices of the kind specified, is that ofensuring effective sealing or quasi-sealing of the edge of said aperturecommunicating with the sample chamber with respect to the slide. TheApplicants have proposed, in co-pending UK Patent Application No.0301047.7 to use an elastomeric gasket around said aperture to effect aseal with respect to the slide. However, in the past, it has been commonto interpose between the slide and the base of the device in which thesaid aperture is provided, a sheet of liquid-absorbent paper or card,with a hole therein which is aligned with the aperture in said base ofthe centrifugation device and which serves to absorb liquid from thesample whilst blocking passage of cells, etc. which are to be depositedon the slide. Such a filter card arrangement is still preferred forsmall capacity centrifugation devices of the kind specified. However,because of limited compressibility of the filter card paper used,correct alignment of the surface of the said base which in the closedposition provides engages the and provides support for the filter cardheld against the slide surface, good alignment of that surface with theopposing slide surface is necessary if leakage of fluid, (and/or cellmaterial) past the filter card is to be avoided.

It is an object of the present invention to provide an improvedcentrifugation device.

According to one aspect of the invention there is provided acentrifugation device comprising a combined sample chamber and slideholder adapted to be mounted, with a microscope slide, in a centrifugein a predetermined position, after placing, in the sample chamber, afluid biological sample containing cells, the centrifugation devicecomprising a body affording a base adapted for engagement with amicroscope slide, structure on one side of the base defining a chamberfor a fluid sample, with an opening for the introduction of fluid tosaid chamber, the base including an aperture and carrying a means forsealing the edges of such aperture with respect to the surface of amicroscope slide placed across the base, or for allowing the passage ofliquid but obstructing the passage of cells, the centrifugation devicefurther including a back plate arranged, when the back plate is closedagainst the rear of a microscope slide engaged with the base, to locatethe slide between the base and the cover plate and to hold the coverplate in this closed position, wherein said base comprises a supportingframe and, within said supporting frame, a pressure plate provided withsaid aperture, and wherein the pressure plate is supported from saidframe by flexible resilient means such as to allow the pressure plate to“float” and to align itself with a microscope slide located between thepressure plate and the back plate as the back plate is closed.

An embodiment of the invention is described below by way of example withreference to the accompanying drawings in which:—

FIG. 1 is a perspective view from the rear, of a centrifugation devicein accordance with the invention in a condition in which a back plate isopen relative to a body part, the body part being fitted with a filtercard.

FIG. 2 is a rear elevation view to a larger scale of the centrifugationdevice of FIG. 1, also in the open condition, with the filter cardomitted,

FIG. 3 is a perspective view corresponding to FIG. 1 but with the filtercard omitted,

FIG. 4 is a partial view in vertical section of the body part of thedevice of FIGS. 1 to 3, and

FIG. 5 is a partial perspective view, from the rear and above, of thecentrifugation device of FIGS. 1 to 4 in the condition in which the backplate is closed against the body part, with a microscope slide locatedtherebetween.

FIG. 6 is a perspective view, with a back plate in an open position, ofa variant of the centrifugation device of FIGS. 1 to 4.

Referring to FIGS. 1 to 5, a centrifugation device in accordance withthe present invention comprises a body part 10 and a back plate 12formed integrally with one another by moulding in a suitable plasticsmaterial such as polypropylene, the back plate 12 being connected withthe body part 10 by way of an integral “living hinge” 22. As shown inFIGS. 1 to 5, the body part 10 comprises a base 14 which, as describedbelow, comprises a frame 17 bounding a plate 19 which carries on itsfront side integral structure providing a sample chamber 16 which isclosed at its end remote from the base 14 and which terminates, in theplane of the plate 19, in an aperture or port 18. A funnel 15 extendsupwardly from an entrance opening in the sample chamber, whereby a fluidsample can be introduced into the sample chamber 16.

The base 14 is generally rectangular, as is the back plate 12, and theliving hinge 22 extends along one vertical edge of the base 14, moreparticularly along one vertical edge of the frame 17, and the adjacentvertical edge of the back plate 12. The vertical edge of the back plate12 remote from the living hinge 22 carries a detent 24 for co-operatingwith elements 25 carried by the body 10 adjacent the edge of the base 14remote from the living hinge 22 and which elements, together with detent24, form a catch arrangement whereby the back plate may be secured in aclosed position on the base 14 with a microscope slide, indicated at 26in FIG. 5, held between the base 14 and the back plate 12. Asillustrated, the upper edge of the back plate 12 may be scalloped orrecessed, as indicated, to allow ready grasping of the upper edge of themicroscope slide 26 between finger and thumb during removal of the slidefrom the device after centrifugation, as described below. A filter card20 is fixed to the rear surface of frame 17 and extends over the plate19. The filter card 20 comprises a sheet of liquid-absorbent card orpaper, which is secured, for example, by ultrasonic welding, at itsupper and lower ends, (as viewed in FIG. 1) to the frame 17 and extendsover the counter plate 19. The filter card 20 has an aperture 21 thereinwhich corresponds in size, shape and position to the port 18 and isaligned therewith.

In use of the device, a microscope slide 26 is located between the backplate 12 and the filter card on the base 14. (FIGS. 1 to 3 show integrallugs 31 to support the lower end of a microscope slide 26 fitted againstthe front surface of the back plate 12 until the back plate 12, with theslide, is closed against the base 14).

The device is then mounted in a centrifuge (not shown) in such a mannerthat bosses 30 projecting from the sides of the back plate act asjournals received in bearings provided by complementary slots inmounting structure within the centrifuge. When the centrifuge is atrest, the device rests in the centrifuge in a position in which theslide 26 is at an angle. When the centrifuge is spun up, the devicepivots about the axis of bosses 30, into a position in which the slideis vertical. When the centrifuge is spun, the centrifugal forcegenerated produces a rapid settling of the cells within the biologicalsample against the surface of the glass slide 26, within an area boundedby the edges of port 18 and the aperture 21 in the card 20 and thesecells remain in a thin layer on the slide after the centrifuge isstopped. After the centrifuge is stopped, the centrifugation device isremoved from the centrifuge, and the slide carefully removed afteropening of the back plate. The catch arrangement 24,25 is preferably sodevised, for example as described in our co-pending UK PatentApplication GB0301047.7, that the process of opening the back platefractures part of the catch arrangement and ensures that thecentrifugation device cannot be re-used.

As noted above, the base 14 comprises a peripheral frame 17 and acentral panel or counter plate 19 which is mounted with respect to theframe 17 in such a manner as to allow movement of the counter plate 19with respect to the frame 17. Both the frame 17 and the counter plate 19have substantially planar rearwardly facing surfaces, i.e. surfaceswhich face away from the sample chamber 16, and in the unstressedcondition of the counter plate 19 and the mounting means therefor, therear surface of the counter plate is generally parallel with but spacedslightly rearwardly of the plane of the rear surface of the frame 17, asshown in FIG. 4. The sample chamber 16 and funnel 15 are preferablysubstantially rigid with counter plate 19 and can move slightly, withthe counter plate 19, relative to the peripheral frame 17.

Ideally, in the closed condition of the device, in order to ensure thatthere is no gap between the filter card and the edge of the port 18 orbetween the filter card in the region around the aperture 21 and theslide 26, through which the cell component of the sample as well as theliquid component might leak, the slide should bear evenly on the filterpaper all around the periphery of the aperture 21 and the part of thecounter plate around the aperture 18 should likewise bear evenly againstthe filter paper. Thus, ideally, the relevant parts of the counter plateand the slide, and the portions of the back plate bearing against theslide, should be substantially parallel with one another to achieve thiscondition. Furthermore, in the regions, of the apertures 18 and 21,there should be controlled force pressing the slide against the filtercard and hence against the counter plate. In order to achieve theseconditions despite inevitable manufacturing tolerances, the counterplate 19, as mentioned above, is mounted within the frame 17 in such away as to allow the counter plate to “float” i.e. to adjust its positionslightly in relation to the frame 17. As best shown in FIG. 2, this isachieved as follows.

The frame 17 takes the form of a generally rectangular plate whichpreferably has stiffening structures (not shown in detail), extendingfrom and integral with the front of that plate, i.e. extending generallyin the direction in which the sample chamber extends from the counterplate. The counter plate 19 and the support or suspension means thereforare mounted in a generally rectangular aperture 38 in the frame 17 by arespective torsion bar arrangement 40, 42 respectively at the upper orlower end of aperture 38, (as viewed in FIG. 2), the counter plate 19having a profile complementary with that of the aperture 38 and beingmounted with a generally uniform gap between the side edges of thecounter plate 19 and the adjacent edges of aperture 38 and with a largergap, accommodating the respective torsion bar arrangement, between theupper edge of the plate 19 and the upper edge of the aperture 38 andbetween the lower edge of plate 19 and the lower edge of the aperture38. In the arrangement illustrated, each torsion bar arrangementcomprises a first bar 44, adjacent the respective upper or lower edge ofthe aperture 38 and spanning the aperture 38 from one side edge of thataperture to the other, a second, parallel bar 46, spanning the spacebetween two lugs 48 at the upper corners or two lugs 49 at the lowercorners respectively of the counter plate 19, and an intermediate web50, much narrower than the counter plate 19 and thus extending alongonly over a limited middle portion of the first and second bars 44, 46.

As illustrated in FIG. 4, in the unstressed position of the parts of thedevice, with the back plate 12 in the open position, the rear surface ofthe counter plate 19 is, as previously noted, set rearwardly somewhatrelatively to the rear surface of the frame 17. In this position,however, the rear surface of the counter plate is still generallyparallel with the rear surface of the frame 17. When the back plate ismoved into the closed position with the slide and the filter card 20interposed between the back plate and the counter plate and frame, thefilter card being interposed between the slide and the counter plate 19and frame, the counter plate 19 is displaced forwardly relative to theframe 17 by the pressure applied by the back plate via the slide and thefilter card, this displacement being permitted by resilient twisting andflexing of the torsion bars, particularly the longer torsion bars 44 and46. Should it occur that, due, for example, to manufacturinginaccuracies, the position in which the slide is supported by the backplate in the closed position of the back plate is not precisely parallelwith the rear face of the frame 17, or that, in the unstressed position,the rear face of the counter plate 19 is not quite parallel with therear face of the frame 17, differential flexing of the upper and -lowertorsion bars 44, 46 and, if necessary, a measure of transverse twisting;(i.e. about a vertical axis as viewed in FIG. 2) of the webs 50 of thetorsion bar arrangements, allows the counter plate 19 to align itselfinto perfect register with the slide/filter card combination. The easewith which the counter plate 19 may be twisted about a vertical axis asviewed in FIG. 2 depends largely upon the transverse extent—i.e. theextent parallel with the longer torsion bars—of the webs 50 connectingthe longer and shorter torsion bars 44 and 46 and need generally besomewhat less than the flexibility of each torsion bar arrangement abouthorizontal axes.

Whilst, in the above, the front face of the rear cover and the rear faceof the frame and counter plate have been described as being generallyplanar, it may be advantageous, in order to secure firm clamping of theslide glass and the filter card between the counter plate and the rearcover, to provide, around the port 18, an annular region 180 standingslightly proud of the remainder of the rear surface of the counter plateand to form the back plate 12, as shown, on its forward side, with aplurality of ribs extending horizontally and vertically, with an annularor cylindrical rib 182 positioned for alignment with the annular region180 in the closed position of the back plate, with the front surfaces ofthe horizontal and vertical ribs and the annular region 182 alone lyingin a common plane for engagement with the rear surface of the slide 26.

FIG. 6 illustrates a variant of the device of FIGS. 1 to 5 which differsfrom that of FIGS. 1 to 5 in that there are two sample chambers (notshown) terminating in respective apertures or ports 18 a, 18 b, in thecounter plate 19 and connected with respective funnels (defined bydistinct and mutually isolated parts of a unitary funnel structure 15a). The variant of FIG. 6 is intended to be used with a filter card (notshown) having respective apertures aligned with the ports 18 a, 18 b.

The frame, counter plate and torsion bar arrangements in the embodimentsdescribed are preferably formed in one piece, with the remainder of thecentrifugation device, as a unitary injection moulding in a suitableplastics material such as polypropylene.

1. A centrifugation device comprising a combined sample chamber andslide holder adapted to be mounted, with a microscope slide, in acentrifuge in a predetermined position, after placing, in the samplechamber, a fluid biological sample containing cells, the microscopeslide having a rear, the centrifugation device comprising a bodyaffording a base adapted for engagement with a microscope slide,structure on one side of the base defining a chamber for a fluid sample,with an opening for the introduction of fluid to said chamber, the baseincluding an aperture and carrying a means for sealing the edges of suchaperture with respect to the surface of a microscope slide placed acrossthe base, or for allowing the passage of liquid but obstructing thepassage of cells, the centrifugation device further including a backplate arranged, when the back plate is closed against the rear of amicroscope slide engaged with the base, to locate the slide between thebase and the back plate and to hold the back plate in this closedposition, wherein said base comprises a supporting frame and, withinsaid supporting frame, a pressure plate provided with said aperture, andwherein the pressure plate is supported from said frame by flexibleresilient means such as to allow the pressure plate to “float” and toalign itself with a microscope slide located between the pressure plateand the back plate as the back plate is closed.
 2. A centrifugationdevice according to claim 1 wherein said flexible resilient mountingmeans is such as to allow the pressure plate to tilt about two mutuallyperpendicular axes generally parallel with the plane of the frame, withthe plane of the major surfaces of such microscope slide in the closedposition of the device.
 3. A centrifugation device according to claim 2wherein said resilient flexible suspension means comprises a torsion bararrangement moulded integrally with the remainder of the device.
 4. Acentrifugation device according to claim 1 wherein said resilientflexible suspension means comprises a torsion bar arrangement mouldedintegrally with the remainder of the device.